Winter (2012-13) quarter's lectures are now on iTunesU . This website was retired last quarter, but evidently iTunesU folks still need it for demo code downloads, so the demo code downloads (for this quarter only) have been posted below. Please do not repost these on other websites--they are for the individual use of those of you watching the course on iTunesU. Sorry for the delay! Fall (2011-12) quarter's lectures are also still available on iTunesU and here are its associated downloads (lecture slides and homework assignments).
Mac OS X Developer Library